Sight geometry affects the sight distance available to the driver.  But what about the basics of stop signs?

Two-way stop control

When determining corner sight distance, a setback distance for the vehicle waiting at the crossroad must be assumed.   Setback for the driver of the vehicle on the crossroad has been standardized and they have designed manuals referred to as MUTCD (Manual on Uniform Traffic Control Devices). This manual explains in detail the following:   an intersection is to be a  minimum of 10 feet plus the shoulder width of the major road but not less than 15 feet.  However, the Federal MUTCD requires that a stop line, if used, shall be at least 4 feet from the nearest travel lane.

Line of sight for corner sight distance is to be determined from a 3 ½ foot eye height at the vehicle driver’s location on the minor road to a 4 ¼ foot object height in the center of the approaching lane of the major road.  Corner sight distance is equivalent to a specified time gap at the design speed required for a stopped vehicle to turn right or left.

For passenger vehicles at two lane intersections, this time gap equivalence is commonly a distance 7.5 seconds away at the design speed.  Longer gaps are required for trucks and buses, and for multilane roads.  Generally, the public right-of-way should include and maintain this line-of-sight.

All-way stop control and signalized intersections

Drivers at intersections with all-way stop control or traffic signals need the least sight distance.  At all-way stops, drivers need to be able to see vehicles stopped at the other lanes that they are intersecting with.  At signals, drivers approaching the intersections need to see the signal lights.  In jurisdictions that allow right turn on red, drivers in the right lane stop control need the same sight distance as two-way stop control. For example, the driver making the right turn at a red light. Should come to a complete stop and see what other lanes of traffic are doing. If they cannot safely pull into the intersection making the right turn they should stay stopped. These driver’s do not have the right of way.

Although these things are not needed during normal operations, additional sight distance should be provided for signal malfunctions and power outages. For example, when an area that has lost power has traffic signals that are flashing yellow constantly. All ways of traffic should be acting as if it was an all-way stop control. Everyone should be coming to a complete stop and the first people at the stop should have the right of way to safely enter the intersection.

For more details on this manual the website is https://mutcd.fhwa.dot.gov/

When it comes to hard surfaces for pavement and other similar applications you generally have two choices: asphalt or concrete. Even though both surfaces are similar there are key differences that you should take into account before choosing one or the other.

Some of the considerations you have to take into account when it comes to asphalt vs. concrete are appearance, climate factors, cost and maintenance. Both items have pro and cons.

Asphalt is a flexible pavement, which is used mainly for road construction because of its low cost, and installation time. Asphalt pavement can be driven on the same day it is laid. However, asphalt requires regular maintenance to keep it in good working condition, where concrete does not.

Concrete is a rigid pavement, and is more expensive because it is very labor-intensive to construct. Because concrete is more aesthetically pleasing, it is often used for driveways, patios and other small surface area locations. It can be stamped and colored to mimic wood, stone or other paving alternatives. Concrete is also used on areas that require a strong pavement surface, such as areas that garbage trucks drive over or in loading docks. It is also less susceptible to water and petroleum products, so it is used for drainage solutions (including gutters) and gas stations.

Asphalt Pros and Cons

Asphalt is one the most common materials used for driveways and roads in New England. It is also called blacktop for its color. It is made from a combination of stone and sand fused together from material left over from the production of gasoline, diesel and kerosene.

• Pros of asphalt
  • Relatively cheap (much cheaper than concrete).
  • Preferred in cold climates as it’s less likely to crack and snow removal is easier.
  • Because of its dark color it won’t show stains easily.
  • Repair is easy as it can be repaired or re-layered and does not need to be replaced, up to a point.
  • Can be tinted and sealed.
• Cons of asphalt
  • Somewhat short lifespan.
  • Maintenance is required every few years as it needs to be resealed.
  • Has an oily texture that softens in heat and sunlight.
  • Has rough edges.

Concrete Pros and Cons

Concrete is another hard surface material that is commonly used in driveways and other hard surface applications. Cement is mixed with sand and gravel to create concrete.

• Pros of concrete
  • Lasts a long time, 30-40 years, if constructed properly.
  • Low maintenance as it does not need to be resealed, especially in warmer climates.
  • Better in warm climates as it does not soften.
  • Can be colored and stamped in patterns.
  • Holds up to heavy load bearing vehicles.
• Cons of concrete
  • Prone to cracking, it is expensive and not easy to repair.
  • Salt will damage it. ( it should be sealed if salt is being used)
  • Due to its light color, it stains very easily and shows every color.
  • Cost is very high, even twice as high as asphalt.

Asphalt vs. Concrete – Choose One

If you are looking for a hard surface application, you are going to have to generally decide between these two. So which one should you choose?

• Even though concrete lasts somewhat longer, asphalt costs considerably less and gives more value for your money.
• Concrete will eventually crack, even in warmer climates. There are ways to seal cracks but if they are too large you may end up having to have another slab poured earlier than it should be if small cracks are not sealed early.
• Asphalt can be tinted and made to look very pleasing, similar to concrete.
• Asphalt does not show stains as bad as concrete.
• In areas where it snows, even occasionally, asphalt is easier to deal with for snow removal and treatments to melt ice on the roads. Concrete does not hold up well to some deicers such as salt

Asphalt vs. Concrete – A Close Call

While both surfaces have good and bad traits to them, in north eastern part of America asphalt is the more common choice; unless in heavy load bearing areas. The benefits that asphalt gives you are just a bit better than concrete.

Concrete is not a bad choice by any means and people who use it are generally very happy with it; although it may cause you a few more issues in this area, and it  does cost more than asphalt.

Sited pages:

http://www.braenstone.com/2013/12/asphalt-vs-concrete/

https://www.quora.com/What-are-the-differences-between-concrete-cement-and-asphalt